Recording material processing apparatus or image forming system each of which executes stapling process

A post processing apparatus connectable to an image forming apparatus, the post processing apparatus comprising:

• a conveyance roller pair configured to convey a sheet on which an image is formed by the image forming apparatus;
• a staple tray on which the sheet conveyed by the conveyance roller pair is to be stacked;
• an aligning member pair configured to align a bundle of sheets which are conveyed by the conveyance roller pair and stacked on the staple tray;
• a stapling unit configured to staple the bundle of sheets stacked on the staple tray and aligned by the aligning member pair;
• a sheet discharge tray onto which the bundle of sheets stapled by the stapling unit is discharged through a discharging port,
• wherein the post processing apparatus has a manual stapling mode to staple sheets inserted by a user through the discharging port and placed on the staple tray;
• and
• a notification unit configured to notify the user of a position on the staple tray at which the sheets should be placed in the manual stapling mode.